package com.albedo.java.common.core.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Note: originally released under the GNU LGPL v2.1,
 * but rereleased by the original author under the ASF license (above).
 */

/**
 * <p>A hash map that uses primitive ints for the key rather than objects.</p>
 *
 * <p>Note that this class is for internal optimization purposes only, and may
 * not be supported in future releases of Apache Commons Lang.  Utilities of
 * this sort may be included in future releases of Apache Commons Collections.</p>
 *
 * @author Apache Software Foundation
 * @author Justin Couch
 * @author Alex Chaffee (alex@apache.org)
 * @version $Revision: 905857 $
 * @see java.util.HashMap
 * @since 2.0
 */
class IntHashMap {

	/**
	 * The load factor for the hashtable.
	 *
	 * @serial
	 */
	private final float loadFactor;
	/**
	 * The hash table data.
	 */
	private transient Entry[] table;
	/**
	 * The total number of entries in the hash table.
	 */
	private transient int count;
	/**
	 * The table is rehashed when its size exceeds this threshold.  (The
	 * value of this field is (int)(capacity * loadFactor).)
	 *
	 * @serial
	 */
	private int threshold;

	/**
	 * <p>Constructs a new, empty hashtable with a default capacity and load
	 * factor, which is <code>20</code> and <code>0.75</code> respectively.</p>
	 */
	public IntHashMap() {
		this(20, 0.75f);
	}

	/**
	 * <p>Constructs a new, empty hashtable with the specified initial capacity
	 * and default load factor, which is <code>0.75</code>.</p>
	 *
	 * @param initialCapacity the initial capacity of the hashtable.
	 * @throws IllegalArgumentException if the initial capacity is less
	 *                                  than zero.
	 */
	public IntHashMap(int initialCapacity) {
		this(initialCapacity, 0.75f);
	}

	/**
	 * <p>Constructs a new, empty hashtable with the specified initial
	 * capacity and the specified load factor.</p>
	 *
	 * @param initialCapacity the initial capacity of the hashtable.
	 * @param loadFactor      the load factor of the hashtable.
	 * @throws IllegalArgumentException if the initial capacity is less
	 *                                  than zero, or if the load factor is nonpositive.
	 */
	public IntHashMap(int initialCapacity, float loadFactor) {
		super();
		if (initialCapacity < 0) {
			throw new IllegalArgumentException("Illegal Capacity: " + initialCapacity);
		}
		if (loadFactor <= 0) {
			throw new IllegalArgumentException("Illegal Load: " + loadFactor);
		}
		if (initialCapacity == 0) {
			initialCapacity = 1;
		}

		this.loadFactor = loadFactor;
		table = new Entry[initialCapacity];
		threshold = (int) (initialCapacity * loadFactor);
	}

	/**
	 * <p>Returns the number of keys in this hashtable.</p>
	 *
	 * @return the number of keys in this hashtable.
	 */
	public int size() {
		return count;
	}

	/**
	 * <p>Tests if this hashtable maps no keys to values.</p>
	 *
	 * @return <code>true</code> if this hashtable maps no keys to values;
	 * <code>false</code> otherwise.
	 */
	public boolean isEmpty() {
		return count == 0;
	}

	/**
	 * <p>Tests if some key maps into the specified value in this hashtable.
	 * This operation is more expensive than the <code>containsKey</code>
	 * method.</p>
	 *
	 * <p>Note that this method is identical in functionality to containsValue,
	 * (which is part of the Map interface in the collections framework).</p>
	 *
	 * @param value a value to search for.
	 * @return <code>true</code> if and only if some key maps to the
	 * <code>value</code> argument in this hashtable as
	 * determined by the <tt>equals</tt> method;
	 * <code>false</code> otherwise.
	 * @throws NullPointerException if the value is <code>null</code>.
	 * @see #containsKey(int)
	 * @see #containsValue(Object)
	 * @see java.util.Map
	 */
	public boolean contains(Object value) {
		if (value == null) {
			throw new NullPointerException();
		}

		Entry[] tab = table;
		for (int i = tab.length; i-- > 0; ) {
			for (Entry e = tab[i]; e != null; e = e.next) {
				if (e.value.equals(value)) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * <p>Returns <code>true</code> if this HashMap maps one or more keys
	 * to this value.</p>
	 *
	 * <p>Note that this method is identical in functionality to contains
	 * (which predates the Map interface).</p>
	 *
	 * @param value value whose presence in this HashMap is to be tested.
	 * @return boolean <code>true</code> if the value is contained
	 * @see java.util.Map
	 * @since JDK1.2
	 */
	public boolean containsValue(Object value) {
		return contains(value);
	}

	/**
	 * <p>Tests if the specified object is a key in this hashtable.</p>
	 *
	 * @param key possible key.
	 * @return <code>true</code> if and only if the specified object is a
	 * key in this hashtable, as determined by the <tt>equals</tt>
	 * method; <code>false</code> otherwise.
	 * @see #contains(Object)
	 */
	public boolean containsKey(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				return true;
			}
		}
		return false;
	}

	/**
	 * <p>Returns the value to which the specified key is mapped in this map.</p>
	 *
	 * @param key a key in the hashtable.
	 * @return the value to which the key is mapped in this hashtable;
	 * <code>null</code> if the key is not mapped to any value in
	 * this hashtable.
	 * @see #put(int, Object)
	 */
	public Object get(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				return e.value;
			}
		}
		return null;
	}

	/**
	 * <p>Increases the capacity of and internally reorganizes this
	 * hashtable, in order to accommodate and access its entries more
	 * efficiently.</p>
	 *
	 * <p>This method is called automatically when the number of keys
	 * in the hashtable exceeds this hashtable's capacity and load
	 * factor.</p>
	 */
	protected void rehash() {
		int oldCapacity = table.length;
		Entry[] oldMap = table;

		int newCapacity = oldCapacity * 2 + 1;
		Entry[] newMap = new Entry[newCapacity];

		threshold = (int) (newCapacity * loadFactor);
		table = newMap;

		for (int i = oldCapacity; i-- > 0; ) {
			for (Entry old = oldMap[i]; old != null; ) {
				Entry e = old;
				old = old.next;

				int index = (e.hash & 0x7FFFFFFF) % newCapacity;
				e.next = newMap[index];
				newMap[index] = e;
			}
		}
	}

	/**
	 * <p>Maps the specified <code>key</code> to the specified
	 * <code>value</code> in this hashtable. The key cannot be
	 * <code>null</code>. </p>
	 *
	 * <p>The value can be retrieved by calling the <code>get</code> method
	 * with a key that is equal to the original key.</p>
	 *
	 * @param key   the hashtable key.
	 * @param value the value.
	 * @return the previous value of the specified key in this hashtable,
	 * or <code>null</code> if it did not have one.
	 * @throws NullPointerException if the key is <code>null</code>.
	 * @see #get(int)
	 */
	public Object put(int key, Object value) {
		// Makes sure the key is not already in the hashtable.
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				Object old = e.value;
				e.value = value;
				return old;
			}
		}

		if (count >= threshold) {
			// Rehash the table if the threshold is exceeded
			rehash();

			tab = table;
			index = (hash & 0x7FFFFFFF) % tab.length;
		}

		// Creates the new entry.
		Entry e = new Entry(hash, key, value, tab[index]);
		tab[index] = e;
		count++;
		return null;
	}

	/**
	 * <p>Removes the key (and its corresponding value) from this
	 * hashtable.</p>
	 *
	 * <p>This method does nothing if the key is not present in the
	 * hashtable.</p>
	 *
	 * @param key the key that needs to be removed.
	 * @return the value to which the key had been mapped in this hashtable,
	 * or <code>null</code> if the key did not have a mapping.
	 */
	public Object remove(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
			if (e.hash == hash) {
				if (prev != null) {
					prev.next = e.next;
				} else {
					tab[index] = e.next;
				}
				count--;
				Object oldValue = e.value;
				e.value = null;
				return oldValue;
			}
		}
		return null;
	}

	/**
	 * <p>Clears this hashtable so that it contains no keys.</p>
	 */
	public synchronized void clear() {
		Entry[] tab = table;
		for (int index = tab.length; --index >= 0; ) {
			tab[index] = null;
		}
		count = 0;
	}

	/**
	 * <p>Innerclass that acts as a datastructure to create a new entry in the
	 * table.</p>
	 */
	private static class Entry {
		final int hash;
		final int key; // TODO not read; seems to be always same as hash
		Object value;
		Entry next;

		/**
		 * <p>Create a new entry with the given values.</p>
		 *
		 * @param hash  The code used to hash the object with
		 * @param key   The key used to enter this in the table
		 * @param value The value for this key
		 * @param next  A reference to the next entry in the table
		 */
		protected Entry(int hash, int key, Object value, Entry next) {
			this.hash = hash;
			this.key = key;
			this.value = value;
			this.next = next;
		}
	}

}

